Electric capacitor and stabilized dielectric material therefor



siloxane composition,

ELECTRIC CAPACITOR AND STABILIZED ,DIELECTRIC MATERIAL THEREFOR JosephE. Petley, Troy, N.Y., assignor to General Electric Company, acorporation of New York No Drawing. Application June 24, 1954 SerialNo.439,162

6 Claims. (Cl. 317-259) and having organic radicals attached bycarbon-silicon linkages to at least some of the silicon atoms. Organo- Vprevent changes in .the properties of organo-siloxanes duetothermal,chemical, and electrochemical influences,

' It ano her object of the invention to United States PatentC I ice2,922,938 I Patented Jan. 26, 1,960

and especially capacitors such as tested under to provide usefulstabilizing additives in accordance with the invention. I I

Another group of efl ective stabilizers for the organosiloxanedielectric liquids Was found to be the aromaticaliphatic mono-ketones.is group can be represented by: a 0

Where R may be methyl, ethyl, and long chain aliphatic substituents. Forexample, propiophenone has been found suitable.

A further group of compounds which has been found electrochemicalbreakdown are Especially suitvaluable in stabilizing and prolongingsiloxanes, particularly when used as electrical devices of theabove-mentioned types, is that of the heterocyclic ketones, and of thisgroup beta methyl umbelliferone, also 'known as especially effective.Another example of this group is coumarin.

in traces or very serve as the dielectric liquids.

that amounts of these stabilizer of 0.01-5% by weight based onSpecifically, it is found substances in the range the dielectric liquidare desirableand effective, In particular, the addition of at 0.0004"kraftlpaper with-a 0.00025"aluminum foil d having the following design:3- sheets electrode, andwith effective area of '7 .78 sq.'ft.--havin'ganorninal capacity; of approximately j0.76;-mfd.' 1

It is to be-understood -thatthe following eX'arnpl'esare given for thepurpose of i'llustr'ation only and-are not to be interpretedJaslirniting the scope of the'invention in'any wayn Examplel u- In'thisexample' 'an unstabilized silicone an composed of dimethyl siloxarie-inafnurnber of capacitors 'was tested by subjecting the capacitorsfirst'to 1500 volts undenthese conditions the average life ofthexcapac'itor was foun'd to be 608 hours. When tested "at 1000v. D'.C.at'12S C. the average lifeof the capacitors with'the same composition ofunstabilize'd silicone-oil therein 'was less than 101 hours. V

i I V Example ll A number of capacitors-having adieleetric ,li"uidirnpregnant of dimethyl siloxane incorporating 0. 1 fby weight of'anthraquinone' were tested at 1500 v. DC. and 85 C., the'average-lifeofthe-capacitors under these conditions being 'found-to be 3701 hours.Capacitors having the same stabilized siloxane composition when testedat1000 V. DC. and 125 C. were found to have an average 7 life of 2171hours.

, Example III A seriesof capacitors were. subjected to a life test, thecapacitors having an insulation impregnant composed of dimethyl siloxanehaving an additive therein of 0.1% propiophenone. The capacitors wereoperate "at'1500 v. DC. at 85 C., and under these conditions was foundthat'the average 'life'of the capacitorsftestd was 4971- hours. Whena'group of capacitors having the same composition of insulationimpregnant were subjected to 1000 v. DLC. at 125 C., the averagelife'w'as found to'be 821 hours. a

-' Example 1 V Three capacitors 'having a dielectric'liquid thereincomposed of dim ethyl'siloxane and 0.1% beta chlor anthraquinone' weresubjected to a life test temperature of 85 C- and ,1500 vI--D.C.,andfithe average life of the; capacitors was found .to be 3379 -hours..A group of-capacitors having the same composition of dielectric materialwhen tested at 125 C. and 1000 V. DC. lasted an average of- 1206-hours.1

Similar tests at the corresponding" temperatures and voltages as in thepreceding examplesweremade on a number of capacitorshaving as adielectric composition dimethyl siloxane and 0.1% 'betamethyl'anthraquinone, and in the respective life tests the average life of thecapacitors was 3581 hours at "85" C." and .1500 v. D.C., and 2526 hoursat 125 C. and 1000 V. DC.

i Example Vl Similar tests as 'above were carried out" on; capacitorshavingdimethyl .si'loxaneand'0.1"%'- quinizarine as the dielectriccompounm -and in-these tests;the-averageliteof no. '-(hereina'fterdesi'gnated v; 15.0. at. c., and

the capacitors was found to .be 7579 hours and 208.4 hours,respectively.

Example VII Tests were made on capacitors having dimethyl'siloxane and0.1% of beta amino anthraquinone as a stabilized dielectric liquid undercorresponding temperatures'and potential as above, and the average lifeof the capacitors in these tests was found :to be 1821 hours and 910hours, respectively. a v

' Example VIII Three capacitors'having a dielectric liquid composed ofdimethyl siloxane' and a stabilizer of 0.05% of beta methylurnbelliferone were' tested at 85 C. and 1500 V. DC, and of the threecapacitors, one was found to have a life of 1025 hours, one lasted for2217 hours, and

the third was stillinsatisfactory operating condit-ion after8282.,hours. A similar number of capacitors'withjthe same composition ofdielectric material tested at 125? and 1000 v. BC. was found to have anaverage life of 1395 hours.

Example IX A seriesof capacitors was tested using a dielectricinsulation composition of dimethyl siloxane with a stabilizer of 0.1%ofZ-tertiar'ybutyl anthraquinone, the two testing conditions as in theabove examples prevailing; The

-- life of'these'capacitors wasfound to be, on an average,

5204 hours and 3292 hours,

respectively, under the two testing conditions.

Example X 'ln 'two corresponding accelerated life tests of threecapacitors-having a dielectric of dirnethyl siloxaneplus anadditiveof0.5% dypnone, after 5280 hours "during which thecapacitors'were treated under the conditions of 1500 v. D.C. and 85- C.,all three of the capacitors were found to be in'sat'isfactor'y operatingcondition." When pacitor lasted -for 3167 a similar number of capacitorshaving the same composition of dielectric incorporated thereinw'eretested at C." and 1000 'v. D .C'., the results showedthatone of thecapacitorsdasted for 1526 hours,a second ca hours, and the remaining'fctu pacitor after 4911 'hours'was still operating. .f I I While theinvention has been described with specific referencetoparticularcompounds used in combination with organo-siloxane, dielectric'liquids,it is to b'e'junder stood that it is not'restricted to the recitedcompounds; For example, other compositions within theclasses of chemicalcompoun "mentioned above may be used in accordance with the inventionwithout departing from the spirit or scope of the invention.

Further it is to be understood that whilethesil'icone oils ororganoesiloxanes' referred to herein 'h'ave'been found particularlysuitable for use as dielectric liquids, they are not restricted'to suchuse and may be utilized within the's'cope of'the'inventionfor otherpurposes and applications. For 'exampld 'silicone oils stabilized in accordance with the invention may be use ful as hydraulic fluidsfortransrnission' of'pressure, as damping 'n ledia, and as lubricants,especially where subject to unusual thermal, chemical andelectrochemical conditions. What I claim as new and'desire to secure bylLett'ers- Patentof the United Statesis: 1. An' electric capacitorcomprising, in combination, a hermetically sealed cotainer, a pair ofmetal elec trodesand apaper spacer therebetween in said con ainer, saidpaper spacer being impregnated with a dielectric liquid consistingessentially of an organo siloxane and about .015% by weight of a'ketonesele'cted' from-the group'consisting of anthraquinone andderivativesthereof, propiophenone; dypnone, and beta methylumbelliferone 7 2. The'device as defined in claim 1, wherein the ketonois'a'nthr'aquinone. 1

3. The device as defined in claim 1, wherein the ketone is beta chloranthraquinone.

4. The device as defined in claim 1, wherein the ketone is beta methylanthraquinone.

5. The device as defined in claim 1, wherein the ke- 5 tone isquinizarine.

6. The device as defined in claim 1, wherein the ketone is 2-tertiarybutyl anthraquinone.

References Cited in the file of this patent UNITED STATES PATENTS 62,437,501 Burkhard et a1. Mar. 9, 1948 2,465,296 Swiss et a1. Mar. 22,1949 2,588,436 Violette Mar. 11, 1952 2,802,017 Frost Aug. 6, 1957FOREIGN PATENTS 882,260 Germany Aug. 10, 1953 OTHER REFERENCESStabilization of Chlorinated Diphenyl in Paper Capacitators, byBerberich Industrial and Engineering Chemistry, January 1948, pp.117-123.

Sauer et al.: Stabilization of Dielectrics, Operating Under DirectCurrent Potential, I. & E Chem., vol. 44, No. 1, January 1952, pp.135-140.

1. AN ELECTRIC CAPACITOR COMPRISING, IN COMBINATION, A HERMETICALLYSEALED CONTAINER, A PAIR OF METAL ELECTRODES AND A PAPER SPACERTHEREBETWEEN IN SAID CONTAINER, SAID PAPER SPACER BEING IMPREGNATED WITHA DIELECTRIC LIQUID CONSISTING ESSENTIALLY OF AN ORGANO-SILOXANE ANDABOUT .01-5% BY WEIGHT OF A KETONE SELECTED FROM THE GROUP CONSISTING OFANTHRAQUINONE AND DERIVATIVES THERE OF, PROPIOPHENONE, DYPNONE, AND BETAMETHYL UMBELLIFERONE.